Library of Congress Control Number: 2015917466ģ.2.3 Advanced Techniques for XY (Chain) Selectionįor my lovely and patient wife Tam. The views expressed in this work are solely those of the author and do not necessarily reflect the views of the publisher, and the publisher hereby disclaims any responsibility for them.Īny people depicted in stock imagery provided by Thinkstock are models, and such images are being used for illustrative purposes only.
The views expressed in this work are solely those of the author and do not necessarily reflect the views of the publisher, and the publisher hereby disclaims any responsibility for them.īecause of the dynamic nature of the Internet, any web addresses or links contained in this book may have changed since publication and may no longer be valid. No part of this book may be used or reproduced by any means, graphic, electronic, or mechanical, including photocopying, recording, taping or by any information storage retrieval system without the written permission of the author except in the case of brief quotations embodied in critical articles and reviews. Simplicity itself.SOLVE EXTREME SUDOKU STRATEGIES FOR EASY TO HARD PUZZLESĬopyright © 2015 Scott Gandert & Robert Emmert.Īll rights reserved. And each number inserted into a cage must be unique. The rules for Killer Sudoku are simple – honest! The same rules that govern normal Sudoku apply, but there is an additional killer law: the sum of the cells in a cage must equal the total given for the cage. Mark out how these guesses play out on the Sudoku grid and this will enable you to easily find your way back if you hit a brick wall. The same technique should be employed when you reach the stage where guessing seems to be the only option. Remember Ariadne whose ball of string helped Theseus through the Minotaur’s fiendishly complicated labyrinth? That thread enabled Theseus to backtrack when he reached a dead-end. This is the key to solving harder Sudoku puzzles. The best way is to write them in an imaginary grid of 3x3 – 1, 2, 3 are at the top, and 7, 8, 9 are at the bottom – this will help you scan when you need to spot patterns. Also look at the 3x3 box itself in the context of each line, and you will soon spot other cells for which there is only one possible solution – the lone number.īefore long you will run into a brick wall when the obvious missing numbers run out – at this point it is time to start making notes of the possible candidates in each cell. Sooner or later you will come across numbers which could be placed in a number of different cells: at this stage, make small notes in the cells of its possible number candidates – this will prove useful later on.
The easiest way to begin is to take each number in turn and scan the rows and columns to find cells where that number is missing: you will quickly be able to start putting numbers into cells. Gentle Sudoku, Moderate Sudoku, Tough Sudoku, and Diabolical Sudoku are the four levels that you can choose from depending on your Sudoku skills, ability to stay patient against the odds, and resilience to Sudoku’s mind-bending torment. If you are just starting off then it is worth bearing in mind that both Sudoku and its evil twin the Killer Sudoku are graded by their level of difficulty. To solve Sudoku puzzles you will need every ounce of logic that you can muster. In fact any set of nine distinct symbols – letters, colours, pictures – could be used. Also, contrary to popular opinion, it is not a number puzzle. The reality of solving a Sudoku puzzle grid can stretch the mind of even the most logical amongst us. The rules are deceptively simple: each row, column and 3x3 box of cells must contain each of the numbers 1 to 9.
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